Check out
Apartment Ratings - Apartments for Rent with Ratings and Reviews from Actual Renters (my favorite website when moving to a new place). Looks like only 31% of tenants recommended Southgate Apartments, giving it a rating of 2.17/5.0 I think I'd definitely avoid this one after seeing what others had to say. Here's the direct link to Southgate if you want to read the reviews yourself:
Southgate Towers Apartments Ratings, Reviews, Map, Rents, and other Miami Beach apartments for rent from ApartmentRatings.com
I'm not sure about Flamingo South. Are you referring to the Grand Flamingo on the beach? If so, steer clear of this one too. It's notoriously bad, but lures people in because it appears beautiful and luxurious.
Just as a side note, I moved from the Midwest and was absolutely adamant to live on South Beach because I thought that's where all the fun and excitement was. And damnit, if I was moving to Miami, I was living by the ocean! It's true that South Beach is exciting, but the residences are total slums. Around the ocean is beautiful and nice, but where most people live is absolutely filthy and smelly. I live in a nice apartment in the middle of it all--it seemed perfect with its stainless steel appliances, hardwood floors, and granite countertops--but I have had the sewer overflow into my bathroom 4 times in a week (read: other peoples' crap coming up through my shower drain and toilet). The landlords are notoriously terrible in South Beach and do absolutely nothing about it. It always smells on the streets and there's garbage everywhere. Every time I step outside, I wade through garbage and see 5-6 stray animals at ANY given time. I would never live on South Beach again. I think North Beach is nice, though and doesn't encounter these problems. If you're looking for something truly nice and clean, look elsewhere! I'm moving to Coconut Grove in a couple weeks. You get the same young, vibrant atmosphere, but don't have to deal with the dirty slums that you get on South Beach. I think most others would agree...?